Search results for "critical micelle concentration"
showing 10 items of 64 documents
Micellar liquid chromatography in doping control.
2010
The issue of doping control in sport involves the development of reliable analytical procedures and efficient strategies to process a large number of samples in a short period of time. Reversed-phase LC techniques with aqueous–organic mobile phases and MS or diode-array detection yield satisfactory results for the identification of prohibited substances in sport. However, time-consuming sample pretreatment steps are required, which reduces sample throughput. Micellar LC (MLC) that uses hybrid mobile phases of surfactant above its critical micellar concentration and organic solvent has been revealed as an interesting alternative. The surfactant sodium dodecyl sulfate solubilizes the protein…
Structural and Transport Properties of Bola C-16 Micelles in Water and in Aqueous Electrolyte Solutions
2003
Aqueous solutions containing a bolaform surfactant [R,ω-(4,7,10,13-pentaoxa-16-azacyclooctadecane)- hexadecane], with and without electrolytes have been investigated as a function of surfactant concentration and ionic strength. Small angle neutron scattering (SANS), NMR self-diffusion, and other physical-chemical methods were used. From the analysis of SANS data it was inferred that in water the surfactant forms slightly charged ellipsoidal micelles, because of the partial hydrolysis of amino groups. The aggregates grow with the increase of concentration, becoming more elongated. Due to the selective complexing ability of aza crown ether units, significant differences were observed upon add…
Polymer−Surfactant Interactions. A Quantitative Approach to the Enthalpy of Transfer of Poly(Ethylene Glycol)s from Water to the Aqueous Sodium Perfl…
2000
The enthalpy of transfer (ΔHt) of nonionic polymers at a fixed concentration from water to aqueous substrate solutions as a function of the substrate concentration (fSmS) was determined. The substrates studied are sodium perfluorobutanoate to sodium perfluorooctanoate, and the polymers are poly(ethyleneglycol)s with molecular weights of 400 and 35 000. For the PEG 400-sodium perfluoroheptanoate−water systems, measurements were also performed at some polymer compositions. As a general feature, the enthalpy of transfer steeply changes with fSmS, reaching a maximum beyond which it decreases, tending to level off. A qualitative analysis of the enthalpy data assigned the steep increase of ΔHt to…
Long-term biodistribution study of HPMA- ran -LMA copolymers in vivo by means of 131 I-labeling
2018
Abstract Background For the evaluation of macromolecular drug delivery systems suitable pre-clinical monitoring of potential nanocarrier systems is needed. In this regard, both short-term as well as long-term in vivo tracking is crucial to understand structure-property relationships of polymer carrier systems and their resulting pharmacokinetic profile. Based on former studies revealing favorable in vivo characteristics for 18 F–labeled random (ran) copolymers consisting of N-(2-hydroxypropyl)methacrylamide (HPMA) and lauryl methacrylate (LMA) – including prolonged plasma half-life as well as enhanced tumor accumulation – the presented work focuses on their long-term investigation in the li…
Maleic diamide polymerizable surfactants. Applications in emulsion polymerization
2003
Abstract A series of new polymerizable non-ionic and ionic surfactants (surfmers) with amides groups on both sides of the C=C double bonds have been prepared upon reaction of maleic isoimide carrying a long alkyl chain (or a benzyl group) with a hydrophilic amine derivative. Their critical micellar concentration (CMC) was measured with a surface tensiometer. They have been engaged in batch emulsion polymerization of styrene, and semi-batch seeded copolymerization of styrene and butyl acrylate, giving stable latexes during the polymerization process, and upon extraction with ethanol, showing a high rate of incorporation at the particle surface. However these surfmers do not confer good steri…
Molecular characterization of α,β-poly(N-2-hydroxyethyl)-dl-aspartamide derivatives as potential self-assembling copolymers forming polymeric micelles
2003
A family of graft copolymers derivatives obtained from α,β-poly(N-2-hydroxyethyl)-dl-aspartamide (PHEA) have been studied as potential self-assembling macromolecules forming stable polymeric micelles at low critical micellar concentration. These polymers are obtained grafting on PHEA poly(ethylene glycol) (PEG) (Mw 5000 g/mol) (PHEA–PEG), hexadecylamine (PHEA–C16) or both moieties (PHEA–PEG–C16). The PHEA derivatives were characterised by a multi-angle light scattering (MALS) photometer on line to a size exclusion chromatography system in obtaining the molar mass distribution of the polymers. In addition, to investigate the capacity to form micellar aggregates in aqueous medium the MALS pho…
Linear-dendritic nonionic poly(propylene oxide)–polyglycerol surfactants
2003
Abstract A new type of linear-hyperbranched surfactant has been prepared by anionic ring-opening multibranching polymerization of glycidol onto an end-functional poly(propylene oxide) (PPO) macroinitiator. A hyperbranched, highly hydrophilic polyglycerol block is obtained as the polar segment of the structure. Molecular weights of the nonionic amphiphiles obtained were in the range of 390 to 8,600 g/mol. For comparison, initiators bearing a C16 alkyl chain have also been employed. Furthermore, hyperbranched polyglycerol homopolymers were investigated with respect to amphiphilic properties. All linear-dendritic amphiphiles have been characterized by SEC, DSC, 13 C and 1 H NMR spectroscopy. A…
Temperature triggered self-assembly of polypeptides into multivalent spherical micelles.
2007
We report herein thermally responsive elastin-like polypeptides (ELPs) in a linear AB diblock architecture with an N-terminal peptide ligand that self-assemble into spherical micelles when heated slightly above body temperature. A series of 10 ELP block copolymers (ELP(BC)'s ) with different molecular weights and hydrophilic-to-hydrophobic block ratios were genetically synthesized by recursive directional ligation. The self-assembly of these polymers from unimers into micelles was investigated by light scattering, fluorescence spectroscopy, and cryo-TEM. These ELP(BC)'s undergo two phase transitions as a function of solution temperature: a unimer-to-spherical micelle transition at an interm…
Oligoethyleneoxide spacer groups in polymerizable surfactants
1991
Cationic and zwitterionic polymerizable surfactants bearing tri- and tetraethyleneglycol spacer groups between the polymerizable moiety and the surfactant structure were prepared and polymerized. Monomers and polymers were investigated with respect to their aggregation behavior in aqueous systems and compared to analogous monomers and polymers lacking spacer groups. In the case of the monomeric surfactants, the spacer groups depress both the Kraffttemperature and the critical micelle concentration. the area occupied per molecule at the air-water interface is substantially enlarged by the spacers, whereas the depression of surface tension is nearly constant. Although the monomers with and wi…
Reactions of Maleisomides with Alcohols
2004
Abstract New surfactants (surfmers) with various amide and ester groups next to C˭C double bonds have been obtained. Maleic acid amidesters (AE) with different hydrophobic groups at the nitrogen atom and hydrophilic substituents at oxygen atoms were synthesized starting with maleic isoimides. 1H KMR and IR spectra were used for their characterization. Some were further characterized for their critical micellar concentration (CMC). A few cationic and zwitterionic surfmers were also prepared from isoimide precursors and characterized. All these surfmers were applied in batch emulsion polymerization of styrene, and in core‐shell seeded copolymerization of styrene and butylacrylate to give late…